Put him in his place.

"Master? Apparently you have no idea how to treat one, demon."

"Eh?" Kris's eyes widen and you feel a bit proud for being able to catch him off-guard.

"The way I see it, you already owe me. I'm the one that freed you from that prison," You point to the rather-ignored mirror. "And the way I see it, you actually need me. You acted all high and mighty about wrecking havoc, but you actually don't have enough strength for it yet right? That's why you wanted to make a contract with me. So unless you want to find yourself locked up in here to starve, then you'll learn to treat me with proper respect."

Though you were hiding it well, you were actually a bit scared that he might lash out at you. Instead, an amused grin appears on the demon's face and he bows down to you.

"My apologies. I have to admit that I was looking down on you, but it seems you have a better grasp of the situation than I thought." Oh, you like this. This new attitude of his gives you a strange thrill that you've never felt before. In fact, Kris seems to notice this. "Perhaps instead of Master, it would be more appropriate to call you 'Mistress' instead?"

You feel another thrill run through you. "Yes. From now on you will refer to me as Mistress."

"Now then Mistress, may we please proceed with the contract?"

"Alright. Let's get to it." You nod. And actually, given how high-and-mighty you've been acting you better get this demon under contract quickly before his mood sours. You feel that the demon probably hasn't explaining everything about the contract yet, but if the stories are anything to go by then you know that even a demon can't easily betray a contract once it's made.